Present gasoline stations now include fuel dispensers for dispensing at least three grades or octane levels of gasoline, one of which may be a blend. Typically, a blending dispenser includes alternative dispensing of a high octane fuel, a low octane fuel, and a blend of the two. The blended fuel is a fixed blend predetermined at the gasoline site where the fuel dispenser is located. Such dispensers usually include orifice flow technology, that is orifices of fixed size to control the blend ratio of the typically high and low octane fuels for obtaining the intermediate grade or octane fuel. If it is desired to change the intermediate fuel blend ratio at the site, the changing of orifices is time consuming, and awkward. To overcome this problem, recent fuel dispensing systems have been developed to use proportional flow valves with electronic feedback control in place of the orifices. In such a fuel dispenser, the controller is programmed at the site in order to provide the desired fixed blend of the high and low octane fuels at the fuel dispenser island. In such full three grade multiple product fixed blend fuel dispensers, a total of four flow meters would be typically required for each bank of three hoses, with one fuel meter being required for tracking the volume of fuel dispensed for each one of the low and high octane fuels, and two flow meters being required in the blending operation for the intermediate grade fuel.
One known system for providing dispensing of high and low octane fuels, and a third fixed blended fuel, is the Gilbarco "MPD Fixed Blender" product line (manufactured by Gilbarco Inc., Greensboro, N.C.) This system uses orifice flow technology, and meters the blended fuel.
Another known system for providing a site selectable blended fuel of high and low octane fuels, in combination with dispensing of each of the latter two, is the "Wayne Series 590 Fixed-Ratio Blending Dispenser" (manufactured by Wayne Pump Division of Dresser Industries, Inc., Salisbury, Md.). This system includes stepper motor operated valves for adjusting the flow rates of the fuels being dispensed, and also for adjusting the blend ratio between the high and low fuels for blending the two to provide an intermediate grade fuel.
Many other fuel dispensing apparatus for blending two or more fuels are known in the field of the present invention. One example is Krone et al. U.S. Pat. No. 3,847,302 which teaches the control of a plurality of solenoid operated valves for dispensing a desired blend or grade of gasoline. Preset valve openings are used in Krone in order to provide a predetermined intermediate blend. The valves are preset via the use of needle control secondary valves within one solenoid valve of each one of two pairs of solenoid valves included in a digital valving arrangement. A related system is disclosed in Krone et al. U.S. Pat. No. 3,895,738.
Kierbow et al. U.S. Pat. No. 4,265,266 discloses a system for blending at least two products together. The system includes proportional flow control valves, and closed loop control for at least one of two products being blended. Microprocessor control is utilized for setting the openings of the proportional flow control valves to in turn control hydraulic motors, for controlling pumps in the pumping of liquids being blended together with dry materials, in the example given.
Vetter et al. U.S. Pat. No. 4,440,314 discloses a method and apparatus for blending at least one liquid component, such as a hardener, with a primary lacquer. Closed loop control of the liquids being blended is maintained for controlling the flow rate of one of the liquids to insure maintenance of the desired blend. The speed of pumps pumping the liquids is controlled via feedback from tachometers associated with the pump for providing signals indicating the flow rate of liquid being pumped at any given time.
Shannon U.S. Pat. No. 4,252,253 teaches a drink dispensing apparatus that includes a microprocessor for controlling the pressurization and actuation of pumps to dispense a desired blend of products for obtaining a particular beverage.
Goodwin et al. U.S. Pat. No. 4,083,473 discloses a liquid blending system for providing three grades of fuel, gasoline in the example given, high and low octane grades of gasoline are provided, along with a fixed blend portion of the two. A blend control valve 9 is operated via a first solenoid to one extreme position for dispensing the high grade of gasoline, by another solenoid to an opposite extreme position for dispensing a low grade of gasoline, and is also operated by an electromagnetic clutch for rotating the mechanical control valve to a predetermined intermediate position for dispensing an intermediate grade of fuel having a fixed blend ratio. A closed loop control system monitors flow meters associated with the high and low octane gasolines for maintaining the desired intermediate blend of the two. Lombard U.S. Pat. No. 4,043,300 teaches an apparatus and associated control electronics for comparing the flow rates of air and fuel being delivered to an engine, for controlling a valve setting the flow rate of either the air or the fuel, in order to maintain a desired ratio of air to fuel in mixing the two.
Gulbrandsen U.S. Pat. No. 3,717,283 discloses a gasoline blending apparatus including a low octane gasoline dispenser for dispensing low octane fuel from a storage tank, a premium or high octane gasoline dispenser for dispensing high octane gasoline from a second storage tank, and an intermediate grade gasoline dispenser for dispensing an intermediate grade of fuel that is a blend of the premium and low octane fuels. Two solenoid operated valves are included for permitting high octane fuel to be delivered to a mixing point for mixing with low octane fuel for delivery to the intermediate fuel dispenser whenever such a grade of fuel is selected by a user. The low octane fuel is independently delivered to the low octane dispenser from the storage tank for such fuel. The solenoid operated valves are selectively energized for either permitting only high octane fuel to be delivered to the high octane dispenser, or for permitting high octane fuel to be delivered to a mixing point for mixing with low octane fuel being pumped through to the intermediate dispenser, for providing the intermediate grade of fuel at a given time.
Ernyei U.S. Pat. No. 3,410,293 discloses a system for delivering first and second products to a tank 3, for providing a blend of the products when they are mixed within the tank. Digital flow meters are connected in series with each product supply line to monitor the volume of the associated product being delivered to the tank. A control circuit monitors the output from the respective flow meters for controlling a control valve 14 connected in series with one of the product lines for adjusting the flow rate of that product for maintaining the desired blend of the two products within the tank.
Gross U.S. Pat. No. 3,229,077 teaches a similar system to Ernyei U.S. Pat. No. 3,410,293, for monitoring the flow rate of two fluids, and adjusting the flow rates of one of the fluids via control of a servo valve in series with the product line for the one fluid, for maintaining a desired blend of the two fluids.